Recognizing the KCNV2-Related Retinal Phenotype

Zelinger et al highlight the KCNV2-related retinal phenotype (“cone dystrophy with supranormal rod response”) as an underdiagnosed condition in the Israeli population. Out of 220 index cases of retinal dysfunction with predominant photopic involvement for whom the authors performed KCNV2 mutation analysis, 5 mutation-positive families were identified—for 2 “cone dystrophy with supranormal rod response” had been diagnosed before genetic testing and for 3 the specific diagnosis had not been suspected. Zelinger et al remind us that standard electroretinogram (ERG) testing of affected patients does not always show the classic supranormal rod response to scotopic flash in this condition and attribute underdiagnosis of the condition to this fact. In their article, ERG tracings of the affected patients are not shown, although latencies and amplitudes for the index cases are provided. Also, ages at time of diagnosis are not mentioned, but in the table ages at time of ERG for the index cases are listed as from 14 to 35 years old; ages at time of diagnosis was presumably sometime after that.